Nearshore and Surf-Zone Morphodynamics: A Global Environmental Model for Predicting Hazards and Changes.
Abstract
This report summarizes the results of a study aimed at improving the predictability of nearshore, beach, and surf-zone hydrodynamic and morphologic assemblages. Analyses were performed on time series, spanning 6.5 years of daily wave data, daily tide range, and daily beach state; 2 years of daily wave groupiness statistics; and 6.5 years of monthly beach and surf zone profile data with the goal of identifying the dominant controls on short-term beach response in order to predict changes. Beach state (the reflective and dissipative extremes and 4 intermediate states) are roughly predictable to a first order in terms of the simple parameter Omega = (H sub b)/(w sub s)T where H sub b is breaker height, w sub s is sand fall velocity and T is wave period. Each of the six beach states has different equilibrium range of Omega values and the direction of change depends on the departure from the equilibrium association. Both tide range and groupiness are statistically significant determinants of beach state. Provided that Omega is within the appropriate range to favor beach states at the reflective end of the sequence, spring tides will favor the reflective or low tide terrace states; the transverse bar and rip state is best developed during neap tides. Higher incident wave groupiness favors the more dissipative states and is the major factor favoring the states with pronounced longshore rhythmicity.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 31, 1985
- Accession Number
- ADA163284
Entities
People
- J. D. Boon Iii
- L. D. Wright
- N. C. Shi
Organizations
- Virginia Institute of Marine Science